Myeloproliferative neoplasm with ETV6-ABL1 fusion: a case report and literature review

Fifth Edition of the World Health Organization Classification of Tumors of the Hematopoietic and Lymphoid Tissues: Acute Lymphoblastic Leukemias, Mixed-Phenotype Acute Leukemias, Myeloid/Lymphoid Neoplasms With Eosinophilia, Dendritic/Histiocytic Neoplasms, and Genetic Tumor Syndromes

This manuscript represents a review of lymphoblastic leukemia/lymphoma (acute lymphoblastic leukemia/lymphoblastic lymphoma), acute leukemias of ambiguous lineage, mixed-phenotype acute leukemias, myeloid/lymphoid neoplasms with eosinophilia and defining gene rearrangements, histiocytic and dendritic neoplasms, and genetic tumor syndromes of the 5th edition of the World Health Organization Classification of Tumors of the Hematopoietic and Lymphoid Tissues. The diagnostic, clinicopathologic, cytogenetic, and molecular genetic features are discussed. The differences in comparison to the 4th revised edition of the World Health Organization classification of hematolymphoid neoplasms are highlighted.

Identification of oral therapeutics using an AI platform against the virus responsible for COVID-19, SARS-CoV-2

Purpose: This study introduces a sophisticated computational pipeline, eVir, designed for the discovery of antiviral drugs based on their interactions within the human protein network. There is a pressing need for cost-effective therapeutics for infectious diseases (e.g., COVID-19), particularly in resource-limited countries. Therefore, our team devised an Artificial Intelligence (AI) system to explore repurposing opportunities for currently used oral therapies. The eVir system operates by identifying pharmaceutical compounds that mirror the effects of antiviral peptides (AVPs)-fragments of human proteins known to interfere with fundamental phases of the viral life cycle: entry, fusion, and replication. eVir extrapolates the probable antiviral efficacy of a given compound by analyzing its established and predicted impacts on the human protein-protein interaction network. This innovative approach provides a promising platform for drug repurposing against SARS-CoV-2 or any virus for which peptide data is available. Methods: The eVir AI software pipeline processes drug-protein and protein-protein interaction networks generated from open-source datasets. eVir uses Node2Vec, a graph embedding technique, to understand the nuanced connections among drugs and proteins. The embeddings are input a Siamese Network (SNet) and MLPs, each tailored for the specific mechanisms of entry, fusion, and replication, to evaluate the similarity between drugs and AVPs. Scores generated from the SNet and MLPs undergo a Platt probability calibration and are combined into a unified score that gauges the potential antiviral efficacy of a drug. This integrated approach seeks to boost drug identification confidence, offering a potential solution for detecting therapeutic candidates with pronounced antiviral potency. Once identified a number of compounds were tested for efficacy and toxicity in lung carcinoma cells (Calu-3) infected with SARS-CoV-2. A lead compound was further identified to determine its efficacy and toxicity in K18-hACE2 mice infected with SARS-CoV-2. Computational Predictions: The SNet confidently differentiated between similar and dissimilar drug pairs with an accuracy of 97.28% and AUC of 99.47%. Key compounds identified through these networks included Zinc, Mebendazole, Levomenol, Gefitinib, Niclosamide, and Imatinib. Notably, Mebendazole and Zinc showcased the highest similarity scores, while Imatinib, Levemenol, and Gefitinib also ranked within the top 20, suggesting their significant pharmacological potentials. Further examination of protein binding analysis using explainable AI focused on reverse engineering the causality of the networks. Protein interaction scores for Mebendazole and Imatinib revealed their effects on notable proteins such as CDPK1, VEGF2, ABL1, and several tyrosine protein kinases. Laboratory Studies: This study determined that Mebendazole, Gefitinib, Topotecan and to some extent Carfilzomib showed conventional drug-response curves, with IC50 values near or below that of Remdesivir with excellent confidence all above R2>0.91, and no cytotoxicity at the IC50 concentration in Calu-3 cells. Cyclosporine A showed antiviral activity, but also unconventional drug-response curves and low R2 which are explained by the non-dose dependent toxicity of the compound. Additionally, Niclosamide demonstrated a conventional drug-response curve with high confidence; however, its inherent cytotoxicity may be a confounding element that misrepresents true antiviral efficacy, by reflecting cellular damage rather than a genuine antiviral action. Remdesivir was used as a control compound and was evaluated in parallel with the submitted test article and had conventional drug-response curves validating the overall results of the assay. Mebendazole was identified from the cell studies to have efficacy at non-toxic concentrations and were further evaluated in mice infected with SARS-CoV-2. Mebendazole administered to K18-hACE2 mice infected with SARS-CoV-2, resulted in a 44.2% reduction in lung viral load compared to non-treated placebo control respectively. There were no significant differences in body weight and all clinical chemistry determinations evaluated (i.e., kidney and liver enzymes) between the different treatment groups. Conclusion: This research underscores the potential of repurposing existing compounds for treating COVID-19. Our preliminary findings underscore the therapeutic promise of several compounds, notably Mebendazole, in both in vitro and in vivo settings against SARS-CoV-2. Several of the drugs explored, especially Mebendazole, are off-label medication; their cost-effectiveness position them as economical therapies against SARS-CoV-2.

ETV6::ABL1-Positive Myeloid Neoplasm: A Case of a Durable Response to Imatinib Mesylate without Additional or Previous Treatment

ETV6::ABL1 rearranged neoplasms are rare hematological diseases. To date, about 80 cases have been reported, including myeloid and lymphoid leukemias. The ETV6 gene codes for an ETS family transcription factor and several fusion partners have been described. When translocated, ETV6 causes the constitutive activation of the partner genes. Here, we report the case of a 54-year-old woman with a cryptic insertion of the 3' region of ABL1 in the ETV6 gene. The patient was first diagnosed with idiopathic hypereosinophilic syndrome, according to the clinical history, conventional cytogenetics, standard molecular analyses and pathologist description. Next generation sequencing of diagnosis samples unexpectedly detected both ETV6::ABL1 type A and B fusion transcripts, which were then confirmed by FISH. The diagnosis was Myeloid/Lymphoid neoplasm with ETV6::ABL1 fusion, and the patient received imatinib mesylate treatment. In a follow-up after more than one year, the patient still maintained the molecular and complete hematological responses. This case highlights the importance of timely and proper diagnostics and prompt tyrosine kinase inhibitor treatment.

Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase fusion genes: A workshop report with focus on novel entities and a literature review including paediatric cases

Myeloid/lymphoid neoplasms with eosinophilia (M/LN-eo) and tyrosine kinase (TK) gene fusions are a rare group of haematopoietic neoplasms with a broad range of clinical and morphological presentations. Paediatric cases have increasingly been recognised. Importantly, not all appear as a chronic myeloid neoplasm and eosinophilia is not always present. In addition, standard cytogenetic and molecular methods may not be sufficient to diagnose M/LN-eo due to cytogenetically cryptic aberrations. Therefore, additional evaluation with fluorescence in-situ hybridisation and other molecular genetic techniques (array-based comparative genomic hybridisation, RNA sequencing) are recommended for the identification of specific TK gene fusions. M/LN-eo with JAK2 and FLT3-rearrangements and ETV6::ABL1 fusion were recently added as a formal member to this category in the International Consensus Classification (ICC) and the 5th edition of the WHO classification (WHO-HAEM5). In addition, other less common defined genetic alterations involving TK genes have been described. This study is an update on M/LN-eo with TK gene fusions with focus on novel entities, as illustrated by cases submitted to the Bone Marrow Workshop, organised by the European Bone Marrow Working Group (EBMWG) within the frame of the 21st European Association for Haematopathology congress (EAHP-SH) in Florence 2022. A literature review was performed including paediatric cases of M/LN-eo with TK gene fusions.

Complex Genomic Rearrangements Involving ETV6::ABL1 Gene Fusion in an Individual with Myeloid Neoplasm

ETV6::ABL1 gene fusion is a rare recurrent genomic rearrangement associated with hematologic malignancies, and frequently occurs with additional anomalies. Due to the opposite chromosome orientations of the ETV6 and ABL1 genes, an oncogenic in-frame ETV6::ABL1 gene fusion cannot be formed by a simple translocation. The molecular mechanism of the ETV6::ABL1 fusion and the significance of co-occurring anomalies are not fully understood. We characterized genomic alterations in an individual with ETV6::ABL1 gene-fusion-positive myeloid neoplasm using various genomic technologies. Our findings uncovered a molecular mechanism of the ETV6::ABL1 fusion, in which a paracentric inversion within the short arm of chromosome 12 (12p) and a translocation between the long arm of a chromosome 9 and the 12p with the inversion were involved. In addition, we detected multiple additional anomalies in the individual, and our findings suggested that the ETV6::ABL1 fusion occurred as a secondary event in a subset of cells with the additional anomalies. We speculate that the additional anomalies may predispose to further pathogenic changes, including ETV6::ABL1 fusion, leading to neoplastic transformation.

Myeloproliferative neoplasm with ABL1/ETV6 rearrangement mimics chronic myeloid leukemia and responds to tyrosine kinase inhibitors

Myeloproliferative neoplasms (MPN) associated with ABL1-ETV6 fusions are rare and poorly characterized. To date, less than 20 cases of ABL1-ETV6+ MPN have been reported. We report a 47-year-old man who presented with MPN with clinicopathologic features resembling chronic myeloid leukemia, but there was no evidence of t(9;22)(p34.1;q11.2) or BCR-ABL1 fusion. Conventional cytogenetics and fluorescence in situ hybridization analysis showed ins(12;9)(p13;q34q34) that led to ETV6-ABL1 fusion. The patient responded well to tyrosine kinase inhibitor therapy and achieved remission for 7 years.

Molecular analysis of more than 140 gene fusion variants and aberrant activation of EVI1 and TLX1 in hematological malignancies

Gene fusions are observed in abnormal chromosomal rearrangements such as translocations in hematopoietic malignancies, especially leukemia subtypes. Hence, it is critical to obtain correct information about these rearrangements in order to apply proper treatment techniques. To identify abnormal molecular changes in patients with leukemia, we developed a multiplex reverse transcriptase polymerase chain reaction (MRT-PCR) protocol and investigated more than 140 gene fusions resulting from variations of 29 prevalent chromosomal rearrangements along with EVI1 and TLX1 oncogenic expression in the presence of optimized primers. The potential of the MRT-PCR method was approved by evaluating the available cell lines as positive control and confirmed by sequencing. Samples from 53 patients afflicted with hematopoiesis malignancies were analyzed. Results revealed at least one chromosomal rearrangement in 69% of acute myeloid leukemia subjects, 64% of acute lymphoblastic leukemia subjects, and 81% of chronic myeloid leukemia subjects, as well as a subject with hypereosinophilic syndrome. Also, five novel fusion variants were detected. Results of this study also showed that chromosomal rearrangements, both alone and in conjunction with other rearrangements, are involved in leukemogenesis. Moreover, it was found that EVI1 is a suitable hallmark for hematopoietic malignancies.

An activating mutation of GNB1 is associated with resistance to tyrosine kinase inhibitors in ETV6-ABL1-positive leukemia

Leukemias harboring the ETV6-ABL1 fusion represent a rare subset of hematological malignancies with unfavorable outcomes. The constitutively active chimeric Etv6-Abl1 tyrosine kinase can be specifically inhibited by tyrosine kinase inhibitors (TKIs). Although TKIs represent an important therapeutic tool, so far, the mechanism underlying the potential TKI resistance in ETV6-ABL1-positive malignancies has not been studied in detail. To address this issue, we established a TKI-resistant ETV6-ABL1-positive leukemic cell line through long-term exposure to imatinib. ETV6-ABL1-dependent mechanisms (including fusion gene/protein mutation, amplification, enhanced expression or phosphorylation) and increased TKI efflux were excluded as potential causes of resistance. We showed that TKI effectively inhibited the Etv6-Abl1 kinase activity in resistant cells, and using short hairpin RNA (shRNA)-mediated silencing, we confirmed that the resistant cells became independent from the ETV6-ABL1 oncogene. Through analysis of the genomic and proteomic profiles of resistant cells, we identified an acquired mutation in the GNB1 gene, K89M, as the most likely cause of the resistance. We showed that cells harboring mutated GNB1 were capable of restoring signaling through the phosphoinositide-3-kinase (PI3K)/Akt/mTOR and mitogen-activated protein kinase (MAPK) pathways, whose activation is inhibited by TKI. This alternative GNB1^K89M-mediated pro-survival signaling rendered ETV6-ABL1-positive leukemic cells resistant to TKI therapy. The mechanism of TKI resistance is independent of the targeted chimeric kinase and thus is potentially relevant not only to ETV6-ABL1-positive leukemias but also to a wider spectrum of malignancies treated by kinase inhibitors.

Myeloid neoplasms with eosinophilia

Molecular diagnostics has generated substantial dividends in dissecting the genetic basis of myeloid neoplasms with eosinophilia. The family of diseases generated by dysregulated fusion tyrosine kinase (TK) genes is recognized by the World Health Organization (WHO) category, “Myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1, or with PCM1-JAK2.” In addition to myeloproliferative neoplasms (MPN), these patients can present with myelodysplastic syndrome/MPN, as well as de novo or secondary mixed-phenotype leukemias or lymphomas. Eosinophilia is a common, but not invariable, feature of these diseases. The natural history of PDGFRA- and PDGFRB-rearranged neoplasms has been dramatically altered by imatinib. In contrast, patients with FGFR1 and JAK2 fusion TK genes exhibit a more aggressive course and variable sensitivity to current TK inhibitors, and in most cases, long-term disease-free survival may only be achievable with allogeneic hematopoietic stem cell transplantation. Similar poor prognosis outcomes may be observed with rearrangements of FLT3 or ABL1 (eg, both of which commonly partner with ETV6), and further investigation is needed to validate their inclusion in the current WHO-defined group of eosinophilia-associated TK fusion-driven neoplasms. The diagnosis chronic eosinophilic leukemia, not otherwise specified (CEL, NOS) is assigned to patients with MPN with eosinophilia and nonspecific cytogenetic/molecular abnormalities and/or increased myeloblasts. Myeloid mutation panels have identified somatic variants in patients with a provisional diagnosis of hypereosinophilia of undetermined significance, reclassifying some of these cases as eosinophilia-associated neoplasms. Looking forward, one of the many challenges will be how to use the results of molecular profiling to guide prognosis and selection of actionable therapeutic targets.

An ETV6-ABL1 fusion in a patient with chronic myeloproliferative neoplasm: Initial response to Imatinib followed by rapid transformation into ALL

We report the case of a 26 year-old patient presenting with a persistent leukocytosis and CML-like marrow but no evidence of a BCR/ABL1 fusion. Molecular cytogenetics revealed that a portion of the ETV6 locus was inserted into the ABL1 locus. An ETV6/ABL1 fusion transcript could subsequently be confirmed. The patient was started on imatinib and went into complete cytomorphological remission. QRT-PCR measurements showed a 4 log reduction of the ETV6/ABL1 fusion. 15 months later, the disease transformed into ALL and the patient expired. Thus, an ETV6/ABL1 fusion positive MPN has the potential to transform very rapidly into ALL.

A novel three-way rearrangement involving ETV6 (12p13) and ABL1 (9q34) with an unknown partner on 3p25 resulting in a possible ETV6-ABL1 fusion in a patient with acute myeloid leukemia: a case report and a review of the literature

Background

Acute myeloid leukemia (AML) is commonly characterized by several chromosomal abnormalities resulting in the formation of chimeric genes that play various roles in leukemogenesis. Translocations resulting in the ETV6-ABL1 fusion gene are rare in AML and other hematologic malignancies with only thirty-two previously reported cases in the literature, five of which were AML.

Findings

Herein, we report the case of a 73-year-old male with acute myeloid leukemia arising from MDS, negative for PDGFRA and PDGFRB, positive for bone marrow eosinophilia, rash, and marked fluid retention, which improved dramatically with imatinib therapy. Conventional cytogenetics revealed a t(3;9)(p25;q34), t(5;18)(q13;p11.2), and additional material of unknown origin at 12p11.2 in 2 out of 10 metaphases analyzed. Interphase FISH studies showed evidence of ETV6 (12p13) and ABL1 (9q34) rearrangements in 41.3 % and 5.7 % of the cells respectively. FISH studies on previously G-banded metaphases showed colocalization of ABL1 and ETV6 signals to the short arm of chromosome 3 at 3p25 suggesting a possible ETV6-ABL1 fusion. Subtelomeric metaphase FISH studies also showed the presence of a subtelomere 3p signal on the long arm of the derivative 9, and no subtelomere 3p signal on the derivative chromosome 12.

Conclusions

These findings suggest a complex rearrangement involving an insertion of ETV6 into 3p25 followed by a reciprocal translocation involving 3p25 and 9q34, resulting in a possible ETV6-ABL1 fusion. This case highlights the importance of FISH to characterize complex rearrangements in myeloid malignancies, particularly those resulting in clinically significant chimeric genes.

Characterization of leukemias with ETV6-ABL1 fusion

To characterize the incidence, clinical features and genetics of ETV6-ABL1 leukemias, representing targetable kinase-activating lesions, we analyzed 44 new and published cases of ETV6-ABL1-positive hematologic malignancies [22 cases of acute lymphoblastic leukemia (13 children, 9 adults) and 22 myeloid malignancies (18 myeloproliferative neoplasms, 4 acute myeloid leukemias)]. The presence of the ETV6-ABL1 fusion was ascertained by cytogenetics, fluorescence in-situ hybridization, reverse transcriptase-polymerase chain reaction and RNA sequencing. Genomic and gene expression profiling was performed by single nucleotide polymorphism and expression arrays. Systematic screening of more than 4,500 cases revealed that in acute lymphoblastic leukemia ETV6-ABL1 is rare in childhood (0.17% cases) and slightly more common in adults (0.38%). There is no systematic screening of myeloproliferative neoplasms; however, the number of ETV6-ABL1-positive cases and the relative incidence of acute lymphoblastic leukemia and myeloproliferative neoplasms suggest that in adulthood ETV6-ABL1 is more common in BCR-ABL1-negative chronic myeloid leukemia-like myeloproliferations than in acute lymphoblastic leukemia. The genomic profile of ETV6-ABL1 acute lymphoblastic leukemia resembled that of BCR-ABL1 and BCR-ABL1-like cases with 80% of patients having concurrent CDKN2A/B and IKZF1 deletions. In the gene expression profiling all the ETV6-ABL1-positive samples clustered in close vicinity to BCR-ABL1 cases. All but one of the cases of ETV6-ABL1 acute lymphoblastic leukemia were classified as BCR-ABL1-like by a standardized assay. Over 60% of patients died, irrespectively of the disease or age subgroup examined. In conclusion, ETV6-ABL1 fusion occurs in both lymphoid and myeloid leukemias; the genomic profile and clinical behavior resemble BCR-ABL1-positive malignancies, including the unfavorable prognosis, particularly of acute leukemias. The poor outcome suggests that treatment with tyrosine kinase inhibitors should be considered for patients with this fusion.

Functional analysis of the SEPT9-ABL1 chimeric fusion gene derived from T-prolymphocytic leukemia

We analyzed the function of a SEPT9-ABL1 fusion identified in a case of T-prolymphocytic leukemia with tyrosine kinase inhibitor (TKI) resistance. Five isoforms with different N-termini, including SEPT9a-ABL1, SEPT9b-ABL1, SEPT9d-ABL1, SEPT9e-ABL1 and SEPT9f-ABL1, were detected in the leukemic cells. All isoforms except SEPT9d-ABL1 are localized in the cytoplasm, undergo autophosphorylation and phosphorylate the downstream targets, STAT-5 and Crkl, and provided IL-3-independence and in vivo invasiveness to 32D cells. Additionally, these SEPT9-ABL1 isoforms were resistant to TKIs in vitro and in vivo, in comparison to BCR-ABL1. These findings demonstrated that SEPT9-ABL1 had oncogenic activity and conferred resistance to TKIs.